Properties of Fire

PROPERTIES OF FIRE
A. Physical Properties
• Fire point- The lowest temperature at which a product produces flammable
vapor to produce sustained combustion after the removal of the primary
source.
• Flash Point- The lowest temperature at which a product produces enough
vapour to produce a flash through the application of a small ignition source
near the surface of the product.
• Ignition temperature- The temperature at which the material is heated to
initiate combustion, once ignited.
• Auto- ignition- The temperature at which the heat evolved by a material
decomposing under the influence of heat is sufficient to bring about
combustion without the application of an external source of ignition.
• The ignition point is that smallest temperature at which a substance
can catch fire ( undergoes combustion )without an external agent.
That said it is clear that this temperature should neither be too low
nor too high.
• If it is too low, it catches fire easily and is thus dangerous !
• If it is too high it can not catch fire easily.
• Ignition temperature for diesel =210 ⁰C (approx)
• Ignition temperature of petrol=270 ⁰C (approx)
• Flammable Limits
The flammability limits are
minimum and maximum
concentration of a gas or vapour in
air which can be ignited and
sustain a self propagating flame.
• The limits are normally expressed
at normal atmospheric
temperatures and pressures.
• Flammable Range- The range of

flammable vapour or gas/air
mixture between the lower and
upper flammable(explosive)
limits.
Specific Gravity
is the ration
of the weight of the
material to the
weight of the equal
volume of water.
Vapour Density
The term used to explain
the weight of the vapours is
“vapour density” the density of
vapours of a gas in relation to that
of hydrogen at same temperature
and pressure. If a gas has a vapor
density of less than one it will
generally rise in air. If the vapor
density is greater than one the gas
will generally sink in air.
NOTE:
Density is usually that of a solid or liquid. It's calculated

by dividing the mass by the volume. Vapour density
refers to a gas or vapour. It's a measure of the mass
compared with an equal volume of hydrogen
Boiling Point
Boiling Point (B.P.) is the temperature where the vapor pressure of a
liquid equals the pressure of its surroundings, and then the liquid changes into
vapor.
• Common petroleum products such as gasoline, kerosene and diesel fuel all
boil but they don't have specific boiling points like water does.
• Catalyst
a substance that can be added to a reaction to increase the reaction rate
without getting consumed in the process. Catalysts typically speed up a reaction
by reducing the activation energy or changing the reaction mechanism.
Vapour Pressure
The lowest temperature at which a liquid at a given temperature in a
closed container will remain in the liquid phase without evaporation.
What happens if you boil petroleum?
If you heat gasoline the naphtha will boil off. Naphtha is
extremely flammable. You can boil gasoline; but, if there is an ignition
source all the vapor would burn and there could be an explosion that
could level and have leveled buildings.
• Naphtha is a toxic kind of raw petrol or gasoline distilled from crude
oil and a raw material for the chemical industry
B. Chemical Properties
• Endothermic reaction- are changes
whereby energy (heat) is absorbed
or is added before the reaction
takes place.
• Exothermic reaction- reactions or

changes that release or give-off
energy (heat) thus they produce
substances with less energy than
the reactants.
Oxidation Combustion/flame
a chemical change in which the manifestation of fire when
combustible material and an oxidizing the fire in its gas-phased
agent reacts. combustion. A matter that is
produced by fire.
NOTE:
• Combustion is a rapid and exothermic reaction that releases large amounts

of energy over a very short period of time in the form of heat and light.
Examples of combustion include burning wood, gasoline, and natural gas.
• Oxidation is slower to be observed and less exothermic reaction that may

or may not release energy, depending on the specific reaction.
Examples: Examples of oxidation include rusting of iron, tarnishing of
silver, and the metabolism of food in the body.
MATERIAL
CLASSIFICATION
Grouping of materials with similar characteristics on flammability,
combustion and extinguishing methods is an effective way for setting the
approach pattern to control the incidents.
Combustible Materials Flammable Material

All materials, such as solids. Most materials are
Gases and liquids are flammable; when ignited, the
combustibles, depending on the product will immediately catch
temperature . A product is called fire, without raising the
combustible when its flashpoint is temperature of the material.
38 degrees C or higher.
Combustible materials is grouped into one of four classifications. These
classes of fuel help to simplify fire fighting methods and techniques.
EUROPIAN CLASSIFICATION OF FUELS US CLASSIFICATION OF FUELS
• Class A -Carbonaceous • Class A -Carbonaceous

substance (solid) substance (solid)
• Class B -Liquids • Class B –Liquids and Gases
• Class C -Gaseous Products • Class C –Electrical Material
• Class D-Light Metals • Class D- Metals
Classification of Fire:
• By knowing the classes of fire a certain material will fall into, you will be able
to make intelligent fire fighting decisions.
A. Based on Cause:
1. Natural Fire
2. Accidental Fire
3. Intentional Fire
B. Based on Fuel- Five (5) Classes of Fire
1.Class A
2. Class B
3. Class C
4.Class D
5. Class K
Types of Liquid
• Liquid defined
Liquids are fluids that do not give rise to more than 40 psia when
heated and to 100degrees F (psia is pound-per-square inch absolute)
Over 40 psia this would be identify the fluid as gas.
• Flammable Liquids
These are liquids with the flashpoint below 37.8 degrees C
(100degrees F) and having a vapor pressure not exceeding 276kpa or
40 psia at (100F)
are substances that have the potential to catch fire easily and burn
rapidly.
CLASS I LIQUIDS
Having a flashpoint below 37.8 degrees C (100degrees F) and subdivided into
the following classes:
• Class IA- any liquid that has a flashpoint below 73 degrees F (22.8 degrees
C), and boiling point (BP) below 100 degrees F (37.8Degrees C).
• Class IB- any liquid that has a flashpoint below 73 degrees F (22.8 degrees
C), and boiling point at or above 100 degrees F (37.8Degrees C).
• Class IC- any liquid that has a flashpoint below 100 degrees F (37.8) but not
below 73 degrees F (22.8 C)
CLASS II LIQUIDS
Combustible Liquid
Liquids that have a flashpoint at or above 100 degrees F (37.8 C) and subdivided into
the following categories:
 Class II- any liquid having a flashpoint at or above 100degrees F (37.8C) and
below 140 degrees F (60degrees C).
 Class IIA- any liquid having a flashpoint at or above 60degrees C (100 degree
F) and below 93.3 degrees C (200 degrees F).
 Class IIIA- any liquid having a flashpoint at or above 140degrees F (60
degrees C) and below 200 degrees F (93.3degrees C).
 Class IIIB- any liquid having a flashpoint at or above 93.3 degrees (200
degrees F).
In some countries. Products are coded and clearly identified especially in
transport carriers. There is no international standard, but applicable codes in
different countries or communities provide useful information.
Types of Flammable Liquids:

• Hydrocarbons are naturally-occurring and form the basis of crude oil, natural gas, coal, and
other important energy sources.
• Alkanes
• Alkenes
• Alkynes
• Aromatics
• Halogenated Carbon also known as halocarbons are fluorine, chlorine, or bromine.
• Alcohol
• Aldehydes
• Amines
• Ethers
• Ketone
• esters
Slopover- refers to the overflow or spillage of a burning liquid when its
container is unable to contain the volume.
BLEVE (Boiling Liquid Expanding Vapor Explosion)

is a dangerous explosion that can occur when the pressurized liquid inside a
vessel, such as a propane tank, reaches temperatures higher than the boiling
point of the liquid . If the vessel fails to contain the pressure due to high
temperatures, it can mechanically fail, resulting in an explosion.
Gases
Gases are classified by their chemical, physical properties and usage.
1. Chemical Properties
Chemical properties of gases are of prime interest to firefighters, as they reflect the ability of the gas to react
within it or with other materials.
The chemical properties of gases may be broken down as follows;
• Flammable gases- are gases that have the potential to explode or ignite when mixed with oxygen and provided
with a source of ignition . These gases can be highly dangerous and require special precautions for storage and
handling.
• Non-Flammable gases- are gases that do not have the ability to ignite or explode when mixed with oxygen and
provided with a source of ignition. These gases are generally considered safe to handle and do not pose a fire
hazard.
• Reactive gases- gases that exhibit high chemical activity and have the ability to undergo chemical reactions with
other substances. These gases can react with various materials, including the surfaces of gas detection systems,
containers, and other substances they come into contact with.
• Toxic gases- are gases that have the potential to cause harm or pose a threat to human health due to their
hazardous properties. These gases can be corrosive, asphyxiating, or have toxic effects when inhaled, ingested, or
come into contact with the skin or eyes. It is important to handle and store toxic gases with proper precautions
to ensure safety.
2. Physical Properties
is the physical behavior of gas both outside its container and when
accidentally released, these are prime interest to firefighters.
The Physical Classification are the following;
• Compressed gases- gases that are stored under high pressure in containers such as cylinders or tanks with a
lower pressure limit of 25 psig (pounds per square inch gauge) at normal temperature of 70 degrees F to 100
degrees F.
• The class of gases that are termed compressed gases are non-liquefied gases. This means that they do
not become liquid at normal temperatures, even at high pressure. They are either:
• Liquified gases- also known as liquid gases, are gases that have been converted into a liquid state through
cooling or compression. This process involves reducing the temperature and/or increasing the pressure of
the gas until it reaches a point where it transitions into a liquid form.
• Examples of liquefied gases include liquid air, liquefied natural gas, and liquefied petroleum gas.
• As pressure is released, the liquid propane vaporizes and turns into gas that is used in combustion.
• Cryogenic gases- Cryogenic gases are gases that are cooled to extremely low temperatures, typically below -
150 degrees Celsius (-238 degrees Fahrenheit), at which point they become liquids. These gases are handled,
transported, and stored in their liquid state at cryogenic temperatures.
• Example: storing large quantities of food, special effects fog, recycling, freezing blood and tissue samples,
and even cooling superconductors.
3. Usage
Classification of gases is made by their usages. However, there
will be much overlapping in these usages
• Fuel gases- gases which burn with air to produce heat, power, or light.
• Industrial gases- gases used in industrial processes such as: water

treatment, welding and cutting, refrigeration and etc.
• Medical Gases- gases used for medical purposes such as therapy and
anesthesia.

Properties of Fire

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PROPERTIES OF FIRE

• Flammable Range- The range of

Density is usually that of a solid or liquid. It's calculated

• Exothermic reaction- reactions or

• Combustion is a rapid and exothermic reaction that releases large amounts

• Oxidation is slower to be observed and less exothermic reaction that may

Combustible Materials Flammable Material

EUROPIAN CLASSIFICATION OF FUELS US CLASSIFICATION OF FUELS

• Class A -Carbonaceous • Class A -Carbonaceous

Types of Flammable Liquids:

BLEVE (Boiling Liquid Expanding Vapor Explosion)

• Industrial gases- gases used in industrial processes such as: water

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